Spinal Curvature Modulation Systems and Methods

ABSTRACT

Spinal curvature modulation systems, methods and related devices and instrumentation are disclosed, which include a flexible tether, a tether tensioning unit and bone anchors for the flexible tether that allow the tether to be secured across multiple vertebrae in a region of treatment. When the flexible tether is attached to multiple vertebrae, it can be used to correct spinal deformities. Tension in the flexible tether is adjustable transcutaneously without invasive surgical procedures by use of remotely driven actuators, such as a magnet-driven motor, or by a small tool insertable through a small incision. Disclosed systems and methods thus allow for multiple adjustments of tether tension, and spinal curvature, over time without repeated, highly invasive, spinal surgeries.

RELATED APPLICATION DATA

This application is a continuation-in-part of U.S. Nonprovisional patentapplication Ser. No. 16/302,733, filed on Nov. 19, 2018, whichapplication was a 371 of international application No. PCT/US17/33592,filed on May 19, 20217, and claimed priority to U.S. Provisional PatentApplication No. 62/338,763, filed on May 19, 2016. Each of theseapplications is incorporated by referenced herein in its entirety.

FIELD OF THE INVENTION

The present disclosure relates generally to orthopedic devices andmethods for correcting or modulating spinal deformities utilizingnon-fusion surgical treatments. More specifically, the disclosurerelates to a non-fusion scoliosis construct which incorporates aflexible tether whose tension can be adjusted by a remotely controlledinternal engine or by other mechanical means in a non-invasive manner.This facilitates the maintenance of corrective forces on the curvatureof the spine without significant invasive surgical intervention.

BACKGROUND

Scoliosis is generally a term used to describe an abnormal curvature ofthe spine, usually in the thoracic or thoracolumbar region. Scoliosis iscommonly broken up into different treatment groups, AdolescentIdiopathic Scoliosis, Early Onset Scoliosis and Adult (degenerative)Scoliosis.

Adolescent Idiopathic Scoliosis (AIS) typically affects children betweenages 10 and 16, and becomes most severe during growth spurts that occuras the body is developing. One to two percent of children between ages10 and 16 have some amount of scoliosis. Of every 1000 children, two tofive develop curves that are serious enough to require treatment. Thedegree of scoliosis is typically described by the Cobb angle, which isdetermined, usually from x-ray images, by taking the most tiltedvertebrae above and below the apex of the curved portion and measuringthe angle between intersecting lines drawn perpendicular to the top ofthe top vertebra and the bottom of the bottom vertebra. The term“idiopathic” means that the exact cause of this curvature is unknown.Some have speculated that scoliosis occurs when, during rapid growthphases, the ligamentum flavum of the spine is too tight and hinderssymmetric growth of the spine. For example, as the anterior portion ofthe spine elongates faster than the posterior portion, the thoracicspine begins to straighten, until it curves laterally, often with anaccompanying rotation. In more severe cases, this rotation actuallycreates a noticeable deformity, wherein one shoulder is lower than theother.

Typically, patients with a Cobb angle of 20° or less are not treated,but are continually followed up, often with subsequent x-rays. Patientswith a Cobb angle of 40° or greater are usually recommended for fusionsurgery. It should be noted that many patients do not receive thisspinal assessment, for numerous reasons. Many school districts do notperform this assessment, and many children do not regularly visit aphysician, so often, the curve progresses rapidly and severely. In AIS,the ratio of females to males for curves under 10° is about one to one,however, at angles above 30°, females outnumber males by as much aseight to one. Fusion surgery can be performed on the AIS patients or onadult scoliosis patients. In a typical posterior fusion surgery, anincision is made down the length of the back and Titanium or stainlesssteel straightening rods are placed along the curved portion. These rodsare typically secured to the vertebral bodies with pedicle screws, in amanner that allows the spine to be straightened. Usually, at the sectiondesired for fusion, the intervertebral disks are removed and bone graftmaterial is placed to create the fusion. Alternatively, the fusionsurgery may be performed anteriorly. A lateral and anterior incision ismade for access. Usually, one of the lungs is deflated in order to allowaccess to the spine from this anterior approach.

In a less-invasive version of the anterior procedure, instead of thesingle long incision, approximately five incisions, each about three tofour cm long are made in several of the intercostal spaces (between theribs) on one side of the patient. In one version of thisminimally-invasive surgery, rods and bone screws are placed and aresecured to the vertebrae on the anterior convex portion of the curve.Once the patient reaches spinal maturity, it is difficult to remove therods and associated hardware in a subsequent surgery, because the fusionof the vertebrae usually incorporates the rods themselves. Standardpractice is to leave this implant in for life. With either of these twosurgical methods, after fusion, the patient's spine is now relativelystraight, but depending on how many vertebrae were fused, there areoften limitations in the degree of flexibility, both in bending andtwisting. As these fused patients mature, the fused section can impartlarge stresses on the adjacent non-fused vertebrae, and often, otherproblems including pain can occur in these areas, sometimesnecessitating further surgery. This tends to be in the lumbar portion ofthe spine that is prone to problems in aging patients. Many physiciansare now interested in non-fusion surgery for scoliosis, which mayeliminate some of the drawbacks of fusion.

One group of patients in which the spine is especially dynamic is thesubset known as Early Onset Scoliosis (EOS), which typically occurs inchildren before the age of five, and more often in boys than in girls.This is a more rare condition occurring in only about one or two out of10,000 children, but can be severe, sometimes affecting the normaldevelopment of organs. Because of the fact that the spines of thesechildren will still grow a large amount after treatment, non-fusiondistraction devices known as growing rods have been developed. Thesedevices are typically adjusted approximately every six months, to matchthe child's growth, until the child is at least eight years old,sometimes until they are 15 years old. Each adjustment requires asurgical incision to access the adjustable portion of the device.Because the patients may receive the device at an age as early as sixmonths old, this treatment requires a large number of surgeries. Becauseof the multiple surgeries, these patients have a high preponderance ofinfection.

In AIS patients, the treatment methodology for those with a Cobb anglebetween 20° and 40° is controversial. Many physicians prescribe a brace(for example, the Boston Brace), that the patient must wear on theirbody and under their clothes 18 to 23 hours a day until they becomeskeletally mature, for example to age 16. Because these patients are allpassing through their socially demanding adolescent years, it is quite aserious prospect to be forced with the choice of either wearing asomewhat bulky brace that covers most of the upper body, having fusionsurgery that may leave large scars and also limit motion, or doingnothing and running the risk of becoming disfigured and possiblydisabled. The patient compliance with brace wearing has been soproblematic that there have been special braces constructed which sensethe body of the patient, and keep track of the amount of time per daythat the brace is worn. Coupled with the inconsistent patient compliancewith brace usage, is a feeling by many physicians that braces, even ifused properly, are not at all effective in treating scoliosis. Thesephysicians may agree that bracing can possibly slow down or eventemporarily stop curve (Cobb angle) progression, but they have notedthat as soon as the treatment period ends and the brace is no longerworn, often the scoliosis rapidly progresses, to a Cobb angle even moresevere than it was at the beginning of treatment up until skeletalmaturity.

In the treatment of patients with AIS, surgeons are leaning more towardsnon-fusion approaches using rigid growing rods. The growth of the rod isconfigured to be consistent with the normal growth pattern of theadolescent patient and the length of the rod is modulated by a magneticsystem via an external magnetic driver in a non-invasive manner. Somesurgeons are now beginning to use flexible tethers instead of rigidrods. In this method, a tether is applied on the convex side of thescoliosis curve using pedicle screws applied posteriorly or laterallyonto each vertebra. The tether is appropriately tensioned to correct thecurvature intraoperatively. As the patient grows, the tension in thetether is adjusted periodically (usually every 6 months) via a surgicalapproach. This procedure requires periodic re-operation subjecting thepatient to an extended recovery period. Therefore, there is a need forspinal construct utilizing flexible tethers with an ability to modulatethe tension of the tether form outside the body in a non-invasivemanner.

Another problem with existing systems, even those employing flexibletethers, is that the tensioning devices and bone anchors could bedifficult for the surgeon to configure and secure to the flexibletether. This can increase surgical procedure time and delay adoption ofotherwise improved treatment devices and techniques. Additionally, giventhe forces sometimes required to be applied to the spine by the tetherit may be difficult to maintain sufficient tether tensile strengthwithout sacrificing flexibility. There thus remains a need in the artfor further improvements in many aspects of available spinal curvemodulation systems.

SUMMARY OF THE DISCLOSURE

In one implementation, the present disclosure is directed to a spinalcurve modulation system for treating spinal curvature along a treatmentregion of the spine. The system includes a flexible tether of sufficientlength to extend across the treatment region of the spine includingacross at least three adjacent vertebral bodies in a cranial-caudaldirection; at least one first bone anchor configured to be fixed to afirst vertebra and to the flexible tether; a tether tensioning unitcomprising a tether interface member rotatable around a rotation axisand a remotely operable rotary drive operatively linked to the tetherinterface member to adjust tension in the flexible tether, said tensionapplied to the flexible tether in a direction perpendicular to therotation axis; and at least one second bone anchor having a longitudinalaxis perpendicular to the rotation axis and configured to fix the tethertensioning unit to a vertebra across the treatment region from at saidat least one first bone anchor; wherein said tether tensioning unit isactuatable to adjust tension in the flexible tether without surgicallyexposing the flexible tether, said at least one first bone anchor orsaid at least one second bone anchor.

Other disclosed embodiments include bone anchors for securing a flexibletether to exert force on a bone. Such bone anchors comprise a threadedbody portion with a tip configured to be screwed into bone and a headportion disposed on the threaded body portion opposite the tip, with thehead comprising means for securing the flexible tether. Embodiments ofmeans for securing the flexible tether include a threaded top formed onthe head portion with an open window defined in the head portion underthe threaded top for passing the tether therethrough, an upwardly openslot extending across the head portion transverse to the open windowwith a tether pin configured to be received in the upwardly open slotextending across the open window, and a tether pin cap with an internalthread configured to engage said threaded top and retain the tether pinin the upwardly open slot. Other embodiments of means for securing theflexible tether comprise two opposed side walls formed in the headportion defining an open slot therebetween and a tether pin extendingacross the open slot between the opposed side wall. The tether pin maybe removable in such embodiments and may be secured by means such asrecesses with detents, recesses or openings receiving an interferencemember such as a gasket or by internal threads.

In another implementation, the present disclosure is directed to amethod of treating an abnormal spinal curvature along a treatment regionof the spine. The method includes providing surgical access to thetreatment region of the spine, the treatment region extending along thespine in a generally cranial-caudal direction and spanning at leastthree adjacent vertebrae; fixing a first bone anchor on a selectedvertebra at a first end of the treatment region; fixing a second boneanchor having a longitudinal axis on a selected second vertebra spacedacross the treatment region from the first bone anchor; fixing at leastone third bone anchor on a selected vertebra between the first andsecond bone anchors; attaching a tether tension adjustment mechanism tothe second bone anchor after fixing the second bone anchor to theselected second vertebra; extending a flexible tether between saidtension adjustment mechanism and the first bone anchor; fixing theflexible tether to the at least one third bone anchor; manipulating saidtension adjustment mechanism to initially tension the flexible tether soas to reposition vertebrae across the treatment region; closing thesurgical access to the treatment region of the spine; andpost-operatively, subsequent to closing the surgical access and withoutreopening or creating new surgical access to the flexible tether or boneanchors, manipulating said tension adjustment mechanism in vivo toperiodically adjust tension in the flexible tether.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show aspectsof one or more embodiments of the invention. However, it should beunderstood that the present invention is not limited to the precisearrangements and instrumentalities shown in the drawings, wherein:

FIGS. 1A-D are illustrations of a spine from a posterior view with atether attached laterally.

FIGS. 2A-D are illustrations of a spine from a posterior view with atether attached posteriorly.

FIG. 3 is an illustration of a vertebra from a posterior view with atether screw attached laterally.

FIG. 4 is an illustration of an exemplary embodiment of a spinalcurvature modulation system.

FIG. 5 is an illustration of an alternate embodiment of a spinalcurvature modulation system.

FIG. 6 is an illustration of an alternate embodiment of a spinalcurvature modulation system.

FIG. 7 is an illustration of an alternate embodiment of a spinalcurvature modulation system.

FIG. 8 is an illustration of an alternate embodiment of a spinalcurvature modulation system.

FIG. 9 is an illustration of an alternate embodiment of a spinalcurvature modulation system.

FIG. 10 is an illustration of an alternate embodiment of a spinalcurvature modulation system.

FIG. 11 is an illustration of an alternate embodiment of a spinalcurvature modulation system.

FIG. 12 is an illustration of an alternate embodiment of a spinalcurvature modulation system.

FIG. 13 is an illustration of an alternate embodiment of a spinalcurvature modulation system.

FIG. 14 is an illustration of an alternate embodiment of a spinalcurvature modulation system.

FIG. 15 is an illustration of a magnetic drive mechanism for adjusting aspinal curvature modulation system.

FIG. 16 is a flow chart illustration of a treatment method for spinalcurvature modulation.

FIG. 17 is a perspective view of a further alternative embodiment of aspinal curvature modulation system according to the present disclosure.

FIG. 17A is a perspective view of tether tensioning unit and bone anchorutilized to fix the tether tensioning unit to a vertebrae according toembodiments described herein.

FIGS. 18, 19, 20, 21, 22, and 23A are perspective views of embodimentsof spinal curvature modulation systems showing alternative positioningin accordance with the present disclosure.

FIG. 23B is a cephalad view of an alternative embodiment of the spinalcurvature modulation system shown in FIG. 23A.

FIG. 23C illustrates posterior positioning of a spinal curvaturemodulation system according to embodiments described herein.

FIG. 24A is a perspective view of an anchor screw for a spinal curvaturemodulation system.

FIG. 24B is a front view of the anchor screw shown in FIG. 24A.

FIG. 24C is a detailed view of the anchor screw shown in FIG. 24B.

FIG. 25A is a perspective view of an alternate anchor screw for a spinalcurvature modulation system.

FIG. 25B is a front view of the anchor screw shown in FIG. 25A.

FIG. 25C is a sectional view of the anchor screw shown in FIG. 25Bthrough line A-A.

FIG. 25D is a detailed view of the anchor screw shown in FIG. 25C in anunlocked position.

FIG. 25E is a detailed view of the anchor screw shown in FIG. 25C in alocked position.

FIG. 26 is a perspective view of a slip screw for a spinal curvaturemodulation system.

FIG. 27 is a perspective view of a slip staple for a spinal curvaturemodulation system.

FIG. 28 is a perspective view of an alternate slip screw for a spinalcurvature modulation system.

FIG. 29A is an illustration of a spine from a posterior view with analternate embodiment of the spinal curvature modulation system attachedlaterally.

FIG. 29B is an illustration of a spine from a lateral view of theembodiment of the spinal curvature modulation system shown in FIG. 29A.

FIG. 30 is a perspective view of an alternate tension adjustmentmechanism for the spinal curvature modulation system.

FIG. 31A is a perspective view of an alternate embodiment of a tensionadjustment mechanism for the spinal curvature modulation system.

FIG. 31B is a perspective view of the tension adjustment mechanism ofFIG. 31A with a housing removed.

FIG. 32A is a perspective view of a globoid worm and spur gearmechanism.

FIG. 32B is a side view of the globoid worm and spur gear mechanismshown in FIG. 32A.

FIG. 33 is a perspective view of a further embodiment of the tetherinterface spool.

FIG. 34 is an exploded view of an alternative anchor screw for thespinal curvature modulation system.

FIG. 35A is a perspective view of the anchor screw shown in FIG. 34.

FIG. 35B is a top view of the anchor screw in FIG. 35A.

FIG. 35C is a cross-sectional view of the anchor screw in FIG. 35Bthrough Line A-A.

FIGS. 36, 37, 38, 39, and 40 are perspective views of alternative anchorscrews for the spinal curvature modulation system.

FIGS. 41, 42, and 43 are perspective views of alternative slip screws.

DETAILED DESCRIPTION

Embodiments described herein are directed to spinal curvature modulationsystems, methods and related devices and instrumentation. In general andas described in greater detail below, embodiments of described systemsinclude a flexible tether, a tether tensioning unit and bone anchors forthe flexible tether that allow the tether to be secured across multiplevertebrae in a region of treatment. Tension in the flexible tether isadjustable transcutaneously with remote devices or with an elongate toolrequiring only a small access incision, typically about 2 cm or less.Embodiments described thus allow for multiple adjustments of tethertension, and spinal curvature, over time without repeated, highlyinvasive, spinal surgeries.

FIG. 1A shows a spine with a given angular deformity with angle alpha.With a lateral approach, screws can be placed into the vertebrae on theconvex side of the curve, above and below the apex. Threaded through thescrews is a flexible tether. This tether is fixed at the topmost andbottommost instrumented vertebrae across a region of treatment, but ifthere are any intermediate instrumented vertebrae, the tether is allowedto slide in eyes formed at the screw heads. How many vertebrae areinstrumented is determined clinically but must be greater than or equalto 2. FIG. 1B shows a tensile force applied to the tether at location(A) and location (C) to correct the deformity. It is not necessary forthe tensile force to be applied at both locations. Tensile force atlocation (A) and/or location (C) will correct the deformity. FIG. 1Cshows an equal and opposite tensile force applied to the tether atlocation (B) to correct the deformity. FIG. 1D shows the same spineafter tension force is applied at location (A), (B) and/or (C). Theangular deformity has been corrected.

FIG. 2A shows a spine with a given angular deformity with angle alpha.With a posterior approach, pedicle screws can be placed into thevertebrae on the convex side of the curve, above and below the apex.Threaded through the pedicle screws is a flexible tether. This tether isfixed at the topmost and bottommost instrumented vertebrae, but if thereare any intermediate instrumented vertebrae, the tether is again allowedto slide in the screw heads. How many vertebrae are instrumented isdetermined clinically but must be greater than or equal to 2. FIG. 2Bshows a tensile force applied to the tether at location (A) and location(C) to correct the deformity. It is not necessary for the tensile forceto be applied at both locations. Tensile force at location (A) and/orlocation (C) will correct the deformity. FIG. 2C shows an equal andopposite tensile force applied to the tether at location (B) to correctthe deformity. FIG. 2D shows the same spine after tension force isapplied at location (A), (B) and/or (C). The angular deformity has beencorrected.

FIG. 3 shows a screw 90 implanted into a vertebra (V). This screw isdesigned such that the tether may be threaded through eye 92 in thescrew head such that the tether is constrained, but may still slide.Screw 90 also may be used to fix the free end of the tether to avertebra by passing the tether through the eye and fastening it back toitself such as with a crimpable ferrule or other cable fixation device.A socket for a driving tool may also be provided on the outer end of thescrew head.

FIG. 4 schematically illustrates an embodiment of a spinal curvaturemodulation system. The system includes a tether tensioning unit 99,which in this example comprises a transcutaneously actuatable drivemechanism including an internal actuator 100 acting through gearbox 101to drive worm gear 102 and tether interface 103. The worm gear in turndrives tether interface 103 to tension or de-tension flexible tether104. In one example, internal actuator 100 may comprise a magnetic motorwith a remotely controllable rotatable magnet, which can be driven by anexternal driver mechanism (see, e.g. FIG. 15). The external drivermechanism may comprise another rotatable magnet and a mechanism forcontrolling the rotation of that magnet, for example an electric motorand control system. An exemplary gear set for gearbox 101 is shown inFIGS. 32A and 32B. In one example, rotation of worm gear 102 rotates atether interface 103 through engagement with meshing spur gear teeth. Inone alternative the teeth of the spur gear may directly engage theflexible tether to form tether interface 103 such that when the spurgear rotates it provides a force on the tether 104 to either increase ordecrease the tension in the tether 104. In an alternative embodiment, aseparate tether engaging member is combined with the spur gear, forexample integrally side by side or disposed on a common shaft, to formtether interface 103. In such an alternative embodiment, the tetherengaging member may be formed as a wheel, disk or other rotatable memberwith a periphery configured to mesh with the material of the flexibletether, such as teeth, spikes, abrasive or other high friction surface.In one example, tether 104 may be formed as a cable, band or ribbon madefrom a braided polymer or metal, for example ultra-high molecular weightpolyethylene (UHMWPE), polyethylene terephthalate (PET), thermoplasticpolycarbonate polyurethane (PCU, e.g., Bionate®) or a multilayeredpolymeric strand comprising low molecular and high molecular weightpolyethylene. Metals employed may comprise stainless steel, titanium andalloys thereof in solid or braided configurations. The tether 104 may bedesigned with a tensile strength higher than 300N. When the tether 104is attached to multiple vertebrae it can be used to correct spinaldeformities as described herein. Flexibility of tether 104 should be atleast sufficient to conform to the existing curvature of the area of thespine to be treated without experiencing plastic deformation, in otherwords, sufficient to maintain resiliency in all modes of operation.

It is to be understood that the embodiments disclosed herein aredisclosed as exemplary embodiments to illustrate, when considered as adisclosure as a whole, the various features, components and steps ofembodiments of the present invention. Each combination of components aswould be understood by persons of ordinary skill in the art based on theteachings herein is not explicitly shown because all possiblecombinations will be appreciated and understood from the embodimentsillustrated. For example, it will be understood that unless otherwisedescribed any disclosed internal actuator, gearbox and drive geardisclosed may be used in any combination to make up a tether tensioningunit in accordance with the teachings of the present disclosure.Similarly, any compatible combination of disclosed tether interface andflexible tether may be used together with any disclosed tethertensioning unit. Thus, it will be understood, for example, that tethertensioning unit 99, while illustrated above as employing a magneticallyactuated internal actuator 100, may also employ any other internalactuator within the scope of the present disclosure.

FIG. 5 schematically illustrates another embodiment of a spinalcurvature modulation system utilizing a flexible band tether in whichtension is controlled by tether tensioning unit 109. In this exemplaryembodiment, the system includes a rotatable magnet 110 as an internalactuator, which can be driven by an external driver mechanism (see,e.g., FIG. 15). The rotation of the magnet 110 drives a gearbox 111which in turn drives a worm gear 112; the worm gear acting as the tetherinterface. The teeth of the worm gear 112 mesh with diagonal cuts in aband tether 113. Rotation of the worm gear 112 provides a force on theband tether 113 to either increase or decrease the tension in the bandtether 113. When the band tether 113 is attached to multiple vertebrae,it can be used to correct spinal deformities.

FIG. 6 schematically illustrates a further embodiment of a spinalcurvature modulation system in which flexible tether tension iscontrolled by tether tensioning unit 119. The system includes anelectric motor 120 as internal actuator which can be driven by anexternally induced current or via subcutaneous power leads (see, e.g.,FIG. 10). A suitable electric motor for this purpose may be one thatprovides power in the range of about 1.0-1.2 W. Alternatively, electricmotor 120 may be replaced with a magnetic drive or other internalactuator as described herein. The rotation of the motor 120 drives agearbox 121 which in turn drives a worm gear 122. Rotation of the wormgear 122 rotates the tether interface, in this example a spur gear 123attached to or integral with spool 124 such that they rotate together.When the spool 124 rotates it provides a force on the tether 125 toeither increase or decrease the tension in the tether 125. When thetether 125 is attached to multiple vertebrae, it can be used to correctspinal deformities.

FIG. 7 schematically illustrates another embodiment of a spinalcurvature modulation system in which flexible tether tension iscontrolled by tether tensioning unit 129. The system includes internalactuator 130 as described in other embodiments which can be driven by,for example, an external driver mechanism (see, e.g. FIG. 15) orinduction or directly delivered current (see, e.g., FIG. 10).Alternatively, a manual drive may be used. The rotation of the internalactuator 130 drives a gearbox 131 which in turn drives a bevel gear 132.Rotation of the bevel gear 132 rotates the tether interface comprising,in this example, a second bevel gear 133 and spur gear 134, which may beattached or integrally formed. Bevel gear 133 is perpendicular from thefirst bevel gear 132 and spur gear 134 is attached to the second bevelgear 133 such that they rotate together. The teeth of the spur gear 134mesh with two flexible tethers 135 which continue in oppositedirections. When the spur gear 134 rotates it provides equal andopposite forces on the two tethers 135 to either increase or decreasethe tension in the tethers 135. When the tethers 135 are attached tomultiple vertebrae, it can be used to correct spinal deformities.

FIG. 8 schematically illustrates a detail of an alternative embodimentof a spinal curvature modulation system. In this example, the systemincludes a rotatable magnet 140 as internal actuator, which can bedriven by an external driver mechanism (see, e.g. FIG. 15). The magnet140 is attached to a housing 141 such that they rotate together. Thehousing is attached to two tethers 142 such that when the housing 141rotates, it provides equal and opposite forces on the two tethers 142 toeither increase or decrease the tension in the tethers 142. When thetethers 142 are attached to multiple vertebrae, it can be used tocorrect spinal deformities.

FIG. 9 schematically illustrates another exemplary embodiment of aspinal curvature modulation system in which flexible tension iscontrolled by tether tensioning unit 149. The system includes arotatable magnet 150 as internal actuator, which can be driven by anexternal driver mechanism (see, e.g., FIG. 15). Once again, as elsewheredescribed herein, other disclosed internal actuators may be substitutedfor the magnetic drive. The rotation of the magnet 150 drives a gearbox151 which in turn drives tether interface 152, in this case formed as athreaded cylinder or other axially rotatable member. As tether interface152 rotates, the threads of the threaded portion (referenced by a planecoincident with the axis of rotation) translate up or down. The threadsof tether interface 152 thus mesh with a flexible tether 153 such thatrotation provides a force on the tether 153 to either increase ordecrease the tension in the tether 153. When the tether 153 is attachedto multiple vertebrae, it can be used to correct spinal deformities.

FIG. 10 schematically illustrates an embodiment of a tether tensioningunit for a spinal curvature modulation system in which an electronicdrive mechanism is provided. A wire coil 160 draws power from anexternally positioned inductive wireless power transfer device 164 tofeed an electric motor 161 to drive a gearbox 162, which in turn can beused in conjunction with mechanisms in the other embodiments describedherein to apply a force on a tether to either increase or decrease thetension in the tether. Alternatively, or additionally, subcutaneousleads 163 may be provided, which can be easily accessed and direct powerapplied thereby. Examples of inductive wireless power transfer systemssuitable for use in embodiments of the present invention are disclosed,for example, in U.S. Pat. No. 6,092,531 and U.S. Patent Publication No.2010/0201315, which are incorporated by reference herein in theirentirety.

FIG. 11 schematically illustrates a detail of another embodiment of aspinal curvature modulation system utilizing a manual, hand-driven drivemechanism. In this example, the internal actuator comprises housing 170,which holds a drive nut 171. Drive nut 171 can be accessed through asmall incision and can be rotated with an elongate manual tool 172configured to engage the internal actuator. The drive nut 171 can beused in conjunction with other internal actuators described herein toprovide redundant drive mechanisms for applying a force on a tether toeither increase or decrease the tension in the tether. As used herein, asmall incision, to permit access of an elongate tool to actuate a manualdrive internal actuator, is an incision generally between about 1-3 cmin length and more typically about 2 cm in length.

FIG. 12 schematically illustrates a further alternative embodiment of aspinal curvature modulation system where a tether tension sensor 180 isintegrated into the tether tensioning unit 181 to measure the tensionapplied to the tether 182. Sensor 180 may comprise a compatible tensionsensing device, such as single roller or multi-roller sensors or directstrain gauge sensors, as may be selected by persons of ordinary skill inthe art based on the teachings herein. Sensor 180 may be configured todirectly sense tension in the flexible tether or it may be positioned tosense torque or force within tether tensioning unit as an indicator oftension in the flexible tether. Tether tensioning unit 181 may compriseany of the magnetic, electronic or manual drive mechanisms as disclosedherein, or other suitable mechanism as may be derived by a person ofordinary skill based on the teachings of the present disclosure.

FIG. 13 schematically illustrates another alternative embodiment of aspinal curvature modulation system in which flexible tether tension iscontrolled by tether tensioning unit 189. The system includes arotatable magnet 190 as an internal actuator, which can be driven by anexternal driver mechanism (see, e.g., FIG. 15). The rotation of themagnet 190 drives a gearbox 191 which in turn drives the tetherinterface, in this example, formed as worm gear 192. The teeth of theworm gear 192 mesh with tooth-shaped cuts in a band tether 193. Rotationof the worm gear 192 provides a force on the band tether 193 to eitherincrease or decrease the tension in the band tether 193. When the bandtether 193 is attached to multiple vertebrae, it can be used to correctspinal deformities.

FIG. 14 schematically illustrates an alternative embodiment of a spinalcurvature modulation system in which flexible tether tension iscontrolled by tether tensioning unit 199. In this example, tethertensioning unit 199 includes a rotatable magnet drive 200 as elsewheredescribed, but may alternatively employ other internal actuators as alsodescribed. The rotation of the magnet 200 drives a gearbox 201 which inturn drives a bevel gear 202. Bevel gear 202 engages the tetherinterface comprising, in this example, a second bevel gear 203 and spurgear 204. Thus, rotation of the bevel gear 202 rotates second bevel gear203 which is perpendicular from the first bevel gear 202. Spur gear 204is attached to the second bevel gear 203 such that they rotate together.The teeth of the spur gear 204 mesh with diagonal cuts in a band tether205. Rotation of the spur gear 204 provides a force on the band tether205 to either increase or decrease the tension in the band tether 205.When the band tether 205 is attached to multiple vertebrae, it can beused to correct spinal deformities.

The use of a gear box 201 between the magnet 200 and the bevel gear 202is highly advantageous for transferring the lower force of the rotatingmagnet to a much higher force required for tensioning the band tether205 to correct deformities of the spine. In one particular embodimentthe gear box 201, bevel gears 202 and 203, and spur gear 204 transfer1000 rotations of the magnet 200 into 1 mm of translation of the tetherband 205. In addition to transferring sufficient force for correctingdeformities of the spine, the gear box 201 and related bevel gears 202and 203 and spur gears 204 are also beneficial in resisting the forcesthe corrected spine will place on the system as it tries to resist thecorrection. The gear box 201, bevel gears 202 and 203 and spur gears 204act as a lock preventing the tension in the tether band 205 fromreversing rotation of the spinal curvature modulation system. A gearboxthat reduces the rotations of the rotating magnet at a ratio ofapproximately 1000 to 1 is beneficial at resisting the forces from thespine. Depending on parameters such as the type and size of the internalactuator, gear reduction ratios in the range of about 300:1 to about5000:1 may be utilized in the gearbox.

FIG. 15 schematically illustrates one exemplary embodiment of anexternal magnetic drive mechanism 300 as may be utilized withmagnetically driven embodiments described herein. In this embodiment,housing 302 contains drive magnet 304 and motor 306 connected to drivemagnet 304 via drive shaft 308. Controller 310 controls the operation ofmotor 306. Controller 310 may include a programmable processor or othercontrol system to permit precise, preprogrammed control, as well asintra-procedural adjustments by the surgeon. Controller 310 may alsoinclude a sensor or other wireless communication device, for example, toreceive tether tension information from a tension sensor such as sensor180, shown in FIG. 12. Further details of suitable magnetic drivemechanisms are disclosed, for example, in U.S. Pat. Nos. 8,915,915 and8,439,915, both of which are incorporated herein in their entirety.

FIG. 16 is a flow chart illustrating one exemplary embodiment of atreatment method 400 according to the present disclosure. As shown inFIG. 16, after an initial patient assessment 402, a determination ismade as to the region to be treated including the vertebrae to betreated and the number and location of pedicle screws to be placed 404.A surgical access is created to the treatment region and bone anchors,typically, pedicle screws or other suitable bone anchors, are thenplaced 406 as determined in the prior step in accordance with standardsurgical procedures. Exemplary bone anchors are illustrated in FIGS. 3,24A and 25A. After placement of the bone anchor is confirmed, one ormore tethers are installed 408 corresponding to the treatment modalitydetermined in the initial assessment. Installation of the tethertypically comprises attachment of a tether-free end to a bone anchor atone end of the treatment region and attachment of the tether tensioningunit to a bone anchor at an opposite end of the treatment region. Whendual acting or opposed tethers are employed, for example as shown inFIGS. 6-8, then the tether tensioning unit may be secured to a boneanchor in a mid-range of the treatment region and tethers secured tobone anchors at opposite ends of the treatment region. Afterinstallation of the tether(s), the tethers are initially tensioned 410.Initial tensioning may be accomplished before closure in order toconfirm proper function. At periodic intervals after healing from theinitial surgery to install the system, the patient is reassessed infollow-up assessments 412. An amount of additional movement isdetermined and corresponding additional or retensioning calculated basedon the determined movement. Re-tensioning is remotely or manuallyeffected 414 without creating a new surgical access to the tether orbone anchors using a drive mechanism appropriate for the installedsystem based on the follow-up assessment. Follow-up assessment andre-tensioning may be repeated as necessary until follow-up assessmentindicates treatment is complete. Thereafter, the installed distractionsystem may be surgically removed 416.

FIG. 17 shows another exemplary spinal curvature modulation systemattached laterally to a spine. The system comprises tether tensioningunit 500, flexible tether 504, a tether interface 502, in this caseformed as a spool, and a tether bone anchor 506 attached to at least twovertebral bodies 508. One tether bone anchor 506 is attached to avertebral body 508 at one end of the flexible tether 504 and tethertensioning unit 500 is attached to a vertebral body 508 at the other endof the flexible tether 504 with a second bone anchor as shown in FIG.17A. The flexible tether 504 is wrapped around the tether spool 502 atone end and is fixed at the tether anchor 506 at the other end. Thetension in the flexible tether 504 is increased or decreased by tethertensioning unit 500 by rotation of the tether spool 502 as was describedabove. Tether tensioning unit 500 can be positioned in any of a numberof locations and still perform its function. Tether tensioning unit 500can be comprised of any of the various elements described in theembodiments shown in FIGS. 4-14.

In FIG. 17, tether tensioning unit 500 is positioned posterior andsuperior in relationship to tether interface 502 as indicated by thespinous process 510 which is on the posterior of the spine. In FIG. 18tether tensioning unit 500 is positioned posterior and inferior totether interface 502 and flexible tether 504. In FIG. 19 tethertensioning unit 500 is positioned anterior and superior to tetherinterface 502. In FIG. 20 tether tensioning unit 500 is positionedanterior and inferior to tether interface 502 and flexible tether 504.In FIG. 21 tether tensioning unit 500 is positioned posterior andlateral to tether interface 502 and flexible tether 504. In FIG. 22tether tensioning unit 500 is positioned anterior and lateral to tetherinterface 502 and flexible tether 504. In FIG. 23A tether tensioningunit 500 is positioned posterior and medial to tether interface 502 andflexible tether 504. The medial location can be better seen in FIG. 23Bwhich shows a cutaway view of the vertebral body 508 revealing tethertensioning unit 500 inside the vertebral body 508. The tether tensioningunit may be attached to the vertebral body by a screw or stapleextending from the mechanism as shown, for example in FIG. 17A. With themedial location, tether tensioning unit itself can have an externalthreaded profile 501 or extending staple arms for direct attachment tothe vertebral body. Tether tensioning unit 500 can also be positionedanterior and medial to the flexible tether 504 (not shown). There aremany reasons a surgeon may select different adjustment mechanismlocations including but not limited to a) preservation of the normalmotion of the adjacent spine segments above or below the spinalcurvature modulation system, b) avoid impingement of any sensitivenearby anatomic member, or c) the desire to have a low profile implantthat does not create any visible change to the patient's outsideappearance. Although FIGS. 17-23C show tether tensioning unit 500located at a caudal end of the treatment region or spine segment beingtreated, tether tensioning unit 500 can alternately be located at thecephalad end or in the middle of the treatment region as previouslydescribed and still be positioned in the various locations describedrelative to the flexible tether 504. With positioning in or proximatethe middle of the treatment region, dual tether devices such as shown inFIGS. 6-8 may be employed.

FIGS. 18-23B also show the spinal curvature modulation system attachedlaterally to the vertebral bodies 508. As previously described, thespinal curvature modulation system can also be attached from theposterior side or posterior-lateral side to the vertebral bodies 508 asshown in FIG. 23C. All of the various locations of tether tensioningunit 500 relative to the spine segment and all of the various positionsrelative to the flexible tether 504 described above with lateralattachment are also possible with the posterior or posterior-lateralattachment location.

FIGS. 24A, B and C show one possible anchor screw 600 for fixing one endof a flexible tether (not shown) to the vertebral body (not shown). Theanchor screw 600 is comprised at one end of a threaded body 602 forattachment to the vertebral body and at the other end a head 604 forsecuring the tether. The head 604 contains a set screw 610 and aclamping plate 608. The head 604 and clamping plate 608 define anopening 606 through which a flexible tether can be inserted. Once thetether has been positioned through the opening 606, the set screw 610can be advanced against the clamping plate 608 until the clamping plate608 compresses the tether against the base of the head 604 securing thetether and preventing any relative motion of the tether relative to theanchor screw 600. The head 604 can have an outer profile that isdesigned to be captured by a screw driving device for the purpose ofadvancing the anchor screw 600 into the vertebral body. Head 604, asshown in FIGS. 24A, B and C, has substantially square outer profile, butany type of profile that is commonly used for capture by a drivingmechanism is possible, including but not limited to hexagonal,octagonal, and star-shaped.

FIGS. 25A-E show an alternative embodiment of an anchor screw 700 forfixing one end of a flexible tether, illustrated here as tether 720, tothe vertebral body (not shown). The anchor screw 700 is comprised at oneend of a threaded body 702 for attachment to the vertebral body and atthe other end a head 704 for securing the tether. The head 704 containsa cam 706 and a cam pin 708. The head 704 and the cam 706 define anopening 710 through which a flexible tether can be inserted. As shown inFIG. 25E once the tether 720 is positioned through the opening 710, thecam 706 can rotate around the cam pin 708 to compress the tether 720against the base 712 of the head 704 securing the tether 720 andpreventing any relative motion of the tether 720 relative to the anchorscrew 700. In general, tension applied to the tether in a direction awayfrom the cam will cause the cam to further tighten on the tether,however, cam 706 may also include a biasing member (not shown) such as atorsional spring that biases the cam 706 against the base 712. Thebiased cam 706 will eliminate the opening 710 but would not be biasedwith a force sufficient to prevent the tether 720 from being advancedpast the biased cam 706 in one direction. In this manner the anchorscrew 700 will allow the tether 720 to be advance in one direction butwill prevent the tether 720 from movement in the other.

FIG. 26 shows an embodiment of a bone anchor formed as a slip screw 800.The slip screw 800 is comprised of a threaded body 802 at one end and ahead 804 at the other end. The head 804 has an opening 806 configured toallow through clearance of the tether (not shown). The slip screw 800 isused to guide the tether relative to the vertebral bodies between thetwo end attachment points of the tether.

FIG. 27 shows an alternative form of bone anchor as a slip staple 820.The slip staple 820 is comprised of one or more staple arms 822 a-b atone end and a head 824 at the other end. The head 824 has an opening 826configured to allow through clearance of the tether (not shown). Theslip staple 820 is also used to guide the tether relative to thevertebral bodies between the two tether end attachment points. It is thesurgeon's preference according to the patient's anatomic size and bonequality to use screws or staples for attachment of the spinal curvaturemodulation system to the patient's vertebral bodies. The stapleattachment method can also be used to attach tether tensioning unit atone end of the tether and the anchor mechanism at the other. It is alsothe surgeon's preference to use slip screws 800 or slip staples 820 atthe vertebral bodies located between the tether's two end attachmentpoints, or to use anchor screws 700 at the vertebral bodies locatedbetween the tether's two end attachment points as well as at one anchorpoint. When slip screws 800 or slip staples 820 are used at theintermediate locations, the tension in the tether will be substantiallyconstant between the two end attachment points. When anchor screws 700are used at the intermediate attachment locations, the tension in thetether will vary between each of the separate anchor segments.

FIG. 28 shows an alternate embodiment of the slip screw 840. The slipscrew 840 is comprised of a threaded body 842 at one end and a head 844at the other end. The head 844 has an opening 846 configured to allowthrough clearance of the tether (not shown). The head 844 also has aslot 848 configured for positioning the opening 846 at varying distancesrelative to the threaded body 842. The varying distance of the opening846 for guiding the tether can be beneficial for preserving spinalkyphosis as is illustrated in FIGS. 29A-B. The spinal curvaturemodulation system is designed to reduce the cobb angle of the spine asdescribed herein.

In FIG. 29A the system is attached to vertebral bodies 508 with tethertensioning unit 500 attached at one end, the anchor screw 800 attachedat the other end and slip screws 840 a-c attached at intermediatelevels. FIG. 29B shows the lateral view where the attachment points ofthe spinal curvature modulation system relative to the vertebral bodies508 are shown to lie approximately on the midline (dashed line) of eachvertebral body 508. The flexible tether 504 passes through the openings846 of the slip screw 840, but the flexible tether 504 is not on thevertebral body 508 midline as the openings 846 are not lined up with thethreaded bodies 842. This allows the flexible tether 504 to induceand/or preserve the kyphotic curvature of the spine in the sagittalplane which is a normal healthy curve while at the same time reducingthe scoliotic curve in the coronal plane which is abnormal. The slipscrews 840 located more in the middle of the spinal curvature modulationsystem can have openings 846 that are more offset from the midline thanslip screws 840 located closer to the end attachment points. Theopenings 846 can be adjustably offset as illustrated in FIG. 28, or theopenings 846 can be offset various non-adjustable fixed distances fromthe threaded body 842. The openings 846 can also be offset from one ormore staple arms 822 a-b rather than from a threaded body 842.

Also shown in FIGS. 29A and B is an optional tether stop 850. One ormore tether stops 850 may be placed on the tether at selected locationsto limit movement of one spine segment as relative to other segmentsacross the treatment region. Tether stop 850 may be formed, for example,as a crimpable bead or ferrule and applied to the tether by the surgeonas needed at the time of installation of the tether and tensioning unit.

As previously described, the two end points, tether tensioning unit 500and anchor device can be attached to the vertebral bodies by a threadedrod, a staple arm or any other common attachment mechanism including butnot limited to bands, expandable rods, and the like. The connectionbetween the anchor device and tether tensioning unit or the anchordevice can be rigid as depicted in FIGS. 25-28 or the connections canallow some articulation or relative range of motion such as through aball and socket type of connection.

FIG. 30 shows another alternative tether tensioning unit 540, which iscomprised of a tether interface spool 542 and a manual internal actuator544. When the manual internal actuator 544 is rotated by an outsideforce (see, e.g., FIG. 11), it rotates the tether interface spool 542through internal gears (e.g., FIGS. 4-11). The tool interface of manualinternal actuator 544 is shown as an external hexagonal shape, but anycommonly used driver shape can be used, including but not limited to aninternal slot, a square shape or star shape, both of which could beeither internal or external or the like.

FIGS. 31A-B show another embodiment of a tether tensioning unit 580 thatis comprised of a manual internal actuator 584, a tether interface spool582, a tension relief device 588, and a housing 586. When the manualinternal actuator 584 is rotated by an outside force, it rotates thetether spool 582 either directly or through internal gears. In FIG. 31Bthe housing 586 has been removed to show an internal ratchet 592 andpawl 590 that allows the tether spool 582 to rotate in one forwarddirection to increase tension but prevents the tether spool 582 fromrotating in the reverse direction to relieve tension. The tension reliefdevice 588 can be actuated to raise the pawl 590 away from the ratchet592 to allow the tether spool 582 to rotate in the reverse direction andrelease tension in the tether. This ratchet and tension releasemechanism is not limited to the manually driven mechanism shown, but canalso be included in the previously described magnet driven tensionadjusting mechanisms. Likewise the actuation of the pawl 590 to allowreverse rotation of the tether spool 582 is not limited to manualactuation but also can be achieved through a second magnetic drivenmechanism, or through an electrically driven mechanism such as but notlimited to a solenoid.

The reduction of tether tension can be achieved by many other mechanismsin addition to this ratchet and pawl system. The tether tension can bereduced automatically when a sufficient tension is reached through aslip clutch type of mechanism. A slip clutch can be designed to releasetether tension to prevent tension from becoming so great that it causesdamage to spinal elements such as ligaments or intervertebral discs.Sensors as previously described can also be positioned at either end ofthe tether or anywhere along the length of the tether to measure thetether tension and prevent excessive tether tension by either sending asignal to automatically open a pawl and ratchet type tension releasemechanism as previously described, or send a signal to an externalcontrol to inform the surgeon and/or the patient that excessive tensionexists which should be reduced through the tension adjustment mechanism.The external controller can be paired wirelessly to other devices suchas computers or smart phones so that a surgeon located remotely can bequickly notified. An internal sensor can be powered by an implantedbattery or by power delivered through induction from an induction sourcelocated externally. The sensor can measure the tension in the tetherdirectly, or it can measure the deflection the tether tension creates inthe tether spool or anchor screw head or it could be located to measurethe bending moment of the anchor screw's threaded body or staple arm.The sensor can also measure a different parameter not directly relatedto tether tension such as the number of rotations of the magnet. In oneparticular embodiment two Hall-effect sensors can be located in theexternal driver on either side of the driving magnet. These sensors candetect the rotation of the implant magnet by subtracting out the signalfrom the driving magnet. In this manner the external controller cancollect data that the internal magnet is rotating as desired. The use ofone or more Hall-effect sensors to measure the rotation of the implantedmagnet can result in a noisy signal as the sensor's measurement of themore proximal control magnet will produce a much higher signal than theweaker signal from the distal implanted magnet. In addition to the useof two Hall-effect sensors to measure magnet rotation, the controllercan also contain a current sensor to measure the amount of current thatis being drawn by the motor rotating the control magnet. When thecontrol magnet is initially rotated by the control motor but notmagnetically coupled to the implanted magnet, a specific amount ofcurrent is drawn by the motor. When the control magnet couples with theimplanted magnet, the load on the motor rotating the control magnetincreases in order to rotate both the control magnet and the coupledmagnet. The measurement of the current drawn by the control motor with acurrent sensor can be used to determine if the control magnet and theimplanted magnet are coupled. On occasion there could be occurrences ofmagnet stalling due to an excessive load on the implanted magnet. Use ofa current sensor will still show an increase in current drawn when thecontrol magnet and implant magnet are coupled but stalled. Thecombination of a current sensor and one or more Hall-effect sensors canhelp to provide information of internal magnet rotation (and thereforetether tension adjustment) regardless of the different conditions suchas magnet coupling or magnet stalling.

FIGS. 32A-B show a gear system 900 comprised of a globoid-shaped wormgear 902 and mating spur gear 904. The contour 906 of the worm gear 902is higher on the ends and lower in the middle. This globoid shape allowsa great force to be transferred from the worm gear to the spur gear forany given nominal diameter of worm and spur gears. The gear system 900can be used in any of the previously described tension adjustingmechanisms to transfer the magnetic (or manual) driving force to thetether. This transfer of greater force is of particular importance in animplanted tension adjusting mechanism as it is important to keep theimplant as small as possible while still delivering sufficient force totension the tether to ensure proper adjustment of the curved spine.

FIG. 33 shows a tether interface spool 592 for use with a tethertensioning unit such as the tether tensioning unit 500 shown in FIG. 17.Tether interface spool 592 comprises an alternative embodiment of tetherinterface 502, also shown in FIG. 17. The tether interface spool 592 iscomprised of two spool end flanges 593 a and 593 b and a spool axel 594.The spool axel 594 contains an open slot 596. The open slot 596 isconfigured for a tether to pass through, such as the flexible tether 504in FIG. 17. One end of the flexible tether 504 can pass through the openslot 596 in the tether interface spool 592 and that end can be fixed tothe tether interface spool 592 with, for example, an adhesive.Alternately, the flexible tether 504 can be fixed to a stop or plug suchas a rod or axel that is larger than the open slot 596. The flexibletether 504 can be crimped to the stop or plug. The flexible tether 504can be attached to the stop or plug with adhesive. As the stop or plugis larger than the open slot 596 it prevents the flexible tether 504attached to the stop or plug from passing through the open slot 596. Theflexible tether 504 can also be wrapped around the stop or plug andattached to itself with adhesive or by sewing the flexible tether 504 toitself. The flexible tether 504 can also pass through the open slot 596and wrap back over half of the spool axel 594. Both the portion of theflexible tether 504 entering the open slot 596 and the portion that iswrapped back over the spool axel 594 can be used as two tethers 142 suchas those shown in FIG. 8. The two tethers 142 can be directed inopposite directions as shown in FIG. 8, or the two tethers 142 can bedirected in the same direction to correct spinal deformities.

FIG. 34 shows another possible anchor screw 1000 for fixing the tetherat one end of the spinal curvature modulation system to a vertebralbody. The anchor screw 1000 is comprised of a screw body 1001, a tetherpin 1010, and a tether pin cap 1020. The anchor body 1001 is comprisedat one end of a threaded body 1002 for attachment to the vertebral bodyand at the other end of a screw head 1004 for securing the tether. Thescrew head 1004 is comprised of an open window 1006 for passing thetether and a threaded top 1008 for engagement of the tether pin cap1020. The tether pin 1010 is comprised of two pin flanges 1014 a and1014 b and a pin axel 1012. The tether pin cap 1020 can include one ormore indented grooves 1022 a and 1022 b that can be engaged with a toolfor both holding the tether pin cap 1020 and for threading the tetherpin cap 1020 onto the threaded top 1008 of the screw body 1001.

FIGS. 35A, 35B, and 35C show the anchor screw 1000 engaging a flexibletether 1120. The flexible tether 1120 is comprised of two portions 1122a and 1122 b. One portion 1122 a passes through the open widow 1006 ofthe screw head 1004 and wraps around the pin axel 1012 of the tether pin1010 and passes back through the open widow 1006 to form the secondportion 1122 b of the flexible tether 1120. The pin axel 1012 is seatedin a top slot 1007 in the screw head 1004 with the pin flanges 1014 aand 1014 b on either side of the screw head 1004. The tether pin cap1020 is threaded onto the threaded tip 1008 of the screw head 1004. Thisconfiguration of tether pin cap 1020, tether pin 1010 with pin flanges1014 a and 1014 b, and top slot 1007 in the screw head 1004 constrainthe tether pin 1010 to the anchor screw body 1001. The anchor screw 1000provides a simple and quick method for securing a flexible tether 1120comprised of two portions 1122 a and 1122 b to a vertebral body. Thetether pin cap 1020 is shown as an open ring, but it can alternatelyhave a top cover that has an engagement feature such as a slot forengaging a tool to rotate the tether pin cap 1020 onto the threaded top1008 of the screw body 1001. The slot can be straight, hexagonal, starshaped, or any manner of configuration commonly used for engaging arotating tool.

FIGS. 36, 37, 38, 39, and 40 show alternative embodiments for anchorscrews that provide a simple and quick method for securing a flexibletether 1120 comprised of two portions 1122 a and 1122 b to a vertebralbody. FIG. 36 shows an alternate anchor screw 2000 comprised of a screwbody 2001 and a tether pin 2010. The screw body 2001 is comprised at oneend of a threaded body 2002 for attachment to the vertebral body and atthe other end of a screw head 2004 for securing the tether. The screwhead 2004 is comprised of an open slot 2006 and two side walls 2014 aand 2014 b on either side of the open slot 2006. Each of the side walls2014 a and 2014 b have a retaining recess 2020, for example formed as adetent, on the inside to engage the ends of the tether pin 2010. Theflexible tether 1120 wraps around the tether pin 2010, and then thetether pin 2010 is placed into the recesses 2020 between the two sidewalls 2014 a and 2014 b of the screw head 2004. The top of the two sidewalls 2014 a and 2014 b can have lead in chamfers 2022 a and 2022 b tohelp guide the tether pin 2010 into the detents 2020. Additionally, thetether pin 2010 can also have chamfers or radii at each end to helpfacilitate or guide the tether pin 2010 into the recesses 2020.

FIG. 37 shows an alternate anchor screw 3000 comprised of a screw body3001 and a tether pin 3010. The screw body 3001 is comprised at one endof a threaded body 3002 for attachment to the vertebral body and at theother end of a screw head 3004 for securing the tether. The screw head3004 is comprised of an open slot 3006 and two side walls 3014 a and3014 b on either side of the open slot 3006. Each of the side walls 3014a and 3014 b have a through hole 3020 a and 3020 b to engage the tetherpin 3010. The first end of the tether pin 3010 is placed through thefirst through hole 3020 a and into the open slot 3006. Then the flexibletether 1120 is guided into the open slot 3006 and wrapped around thetether pin 3010 and back out of the open slot 3006. The first end oftether pin 3010 is then placed into the second through hole 3020 b. Thetether pin 3010 can include one of more retaining gaskets 3012 that areconfigured to engage the inside of the through hole 3020 a and/or 3020 bto hold the tether pin 3010 in place relative to the screw body 3001.The retaining gasket 3012 does not have to hold the tether pin 3010 inplace with a very large force because the tether pin 3010 will be firmlysecured by the flexible tether 1120 once the flexible tether 540 istensioned by the tether tensioning unit 500 (FIG. 17).

FIG. 38 shows an alternate anchor screw 4000 comprised of a screw body4001 and a tether pin 4010. The screw body 4001 is comprised at one endof a threaded body 4002 for attachment to the vertebral body and at theother end of a screw head 4004 for securing the tether. The screw head4004 is comprised of an open slot 4006 and two side walls 4014 a and4014 b on either side of the open slot 4006. Side wall 4014 a has athrough hole 4020, and side wall 4014 b has a threaded hole 4022. Thefirst end of the tether pin 4010 has threads 4012 that are placedthrough the through hole 4020 and into the open slot 4006. Then theflexible tether 1120 is guided into the open slot 4006 and wrappedaround the tether pin 4010 and back out of the open slot 4006. The firstend of the tether pin 4010 is then screwed into the threaded hole 4022.The tether pin 4010 can include an engagement pocket 4013 at the secondend face configured to engage a tool used to rotate the threaded pin4010 into the threaded hole 4022. The threaded hole 4022 can be a blindthreaded hole as shown in FIG. 38 or a through threaded hole.

FIG. 39 shows an alternate anchor screw 5000 comprised of a screw body5001 and a tether pin 5010. The screw body 5001 is comprised at one endof a threaded body 5002 for attachment to the vertebral body and at theother end of a screw head 5004 for securing the tether. The screw head5004 is comprised of an open slot 5006 and two side walls 5014 and 5016on either side of the open slot 5006. Side wall 5014 has a receptacleslot 5018 for receiving one end of the tether pin 5010. Side wall 5016creates a stop that engages the extension wall 5012 at the other end ofthe tether pin 5010. The extension wall 5012 of the tether pin 5010 hasa pivot pin 5005 at one end that is engaged in a pivot hole in the screwhead 5004. The tether pin 5010 is pivoted away from the side wall 5016such that the first end of the tether pin 5010 extends out of thereceptacle slot 5018. The flexible tether 1120 is wrapped around thetether pin 5010 and then the tether pin 5010 is pivoted back such thatthe first end of the tether pin 5010 is captured in the receptacle slot5018 and the extension wall 5012 of the tether pin 5010 is butted upagainst the side wall 5016 of the screw head 5004. The anchor screw 5000is designed to anchor a flexible tether 1120 that extends away from thetether pin 5010 towards the extension wall 5016. Anchor screw 5000 wouldnot anchor a flexible tether 1120 that extended in the other directionbecause a flexible tether 1120 extending away from the extension wall5016 would pivot the tether pin 5010 away from the extension wall 5016and open up the tether pin 5010 on the anchor screw 5000.

FIG. 40 shows an alternate anchor screw 6000 comprised at one end of athreaded body 6002 for attachment to the vertebral body and at the otherend of a screw head 6004 for securing the tether 1120. The screw head6004 is comprised of an open slot 6006 and two side walls 6014 a and6014 b on either side of the open slot 6006. Side wall 6014 b has areceptacle pocket 6020 for receiving one end of the tether pin 6010.Side wall 6014 a has a pivot pin 6005 at one end that is engaged in apivot hole in the screw head 6004. The tether pin 6010 is attached toside wall 6014 a at the other end. The tether pin 6010 and the side wall6014 a pivot away from the side wall 6014 b such that the first end ofthe tether pin 6010 extends out of the receptacle pocket 6020. Theflexible tether 1120 is wrapped around the tether pin 6010 and then thetether pin 6010 and the side wall 6014 a are pivoted back such that thefirst end of the tether pin 6010 is captured in the receptacle pocket6020.

FIG. 41 shows another possible screw body 7001 comprised at one end of athreaded body 7002 for attachment to the vertebral body and at the otherend of a screw head 7004 for securing the tether 1120. The screw body7001 of FIG. 41 is similar to the screw body 1001 of FIG. 34 in that thescrew body 7001 of FIG. 41 is configured to work with tether pin 1010,and a tether pin cap 1020, such as shown in FIG. 34. The screw head 7004is comprised of an open slot 7006 for receiving the tether and anorthogonal slot 7007 for receiving the tether pin 1010. The open slot7006 and orthogonal slot 7007 are bordered by 4 threaded pillars 7014a-d which are configured to engagement of the tether pin cap 1020. Theopen slot 7006 receives the flexible tether 1120 and tether pin 1010 asa combined unit from above without having to pass the flexible tether1120 through the open window 1006 and then around the tether pin 1010 asis required for the screw body in FIG. 34. Having an open slot 7006allows the surgeon to easily attach the tether to the screw body 7001.

It is also desirable for the surgeon to attach the tether to a slipscrew from an open top configuration. FIG. 42 shows a slip screw body8000 comprised at one end of a threaded body 8002 for attachment to thevertebral body and at the other end of a screw head 8004 for guiding thetether. The screw head 8004 is comprised of an open slot 8006 and twoside walls 8014 a and 8014 b on either side of the open slot 8006. Thetop ends of side walls 8014 a and 8014 b are threaded to engage a topcap such as the tether pin cap 1020 shown in FIG. 34. The slip screwbody 8000 is attached to a vertebral body and then the flexible tether1120 is placed into the open slot 8006. The flexible tether 1120 iscaptured in the open slot 8006 by threading the tether pin cap 1020 ontothe threaded top ends of the side walls 8014 a and 8014 b. The open slot8006 and the tether pin cap 1020 combine to create an opening thatconstrains but also provides clearance for the flexible tether 1120.This allows the slip screw to guide the flexible tether 1120 relative tothe vertebral bodies between the two end attachment points of theflexible tether 1120.

FIG. 43 shows an alternate slip screw 9000 comprised of a screw body9001 and a screw cap 9020. The screw body 9001 is comprised at one endof a threaded body 9002 for attachment to the vertebral body and at theother end of a screw head 9004 for guiding the tether. The screw head9004 is comprised of an open slot 9006 and two side walls 9014 a and9014 b on either side of the open slot 9006. The top ends of side walls9014 a and 9014 b are comprised of female threads to engage the malethreads of the screw cap 9020. The slip screw body 9000 is attached to avertebral body and then the flexible tether 1120 is placed into the openslot 9006. The flexible tether 1120 is captured in the open slot 9006 bythreading the screw cap 9020 into the female threaded top ends of theside walls 9014 a and 9014 b. The thread tool receptacle 9022 in one endof the screw cap 9020 is configured to receive a threading tool forthreading the screw cap 9020 into the screw head 9004.

In a further alternative embodiment, an anchor screw may be configuredsubstantially as shown in FIG. 36, 37 or 38, except that the tether pinis integrally formed with the head portion sidewalls such that in thisalternative embodiment the anchor screw is a unitary construction. Suchan embodiment may be employed as an end anchor for the flexible tetherby passing one end under the pivot pin and wrapping the flexible tetheraround the pivot pin, substantially as shown in FIG. 35C for example.Also, the same embodiment may be used as a slip/guide anchor by passingboth ends of the flexible tether underneath the tether pin.

The foregoing has been a detailed description of illustrativeembodiments of the invention. It is noted that in the presentspecification and claims appended hereto, conjunctive language such asis used in the phrases “at least one of X, Y and Z” and “one or more ofX, Y, and Z,” unless specifically stated or indicated otherwise, shallbe taken to mean that each item in the conjunctive list can be presentin any number exclusive of every other item in the list or in any numberin combination with any or all other item(s) in the conjunctive list,each of which may also be present in any number. Applying this generalrule, the conjunctive phrases in the foregoing examples in which theconjunctive list consists of X, Y, and Z shall each encompass: one ormore of X; one or more of Y; one or more of Z; one or more of X and oneor more of Y; one or more of Y and one or more of Z; one or more of Xand one or more of Z; and one or more of X, one or more of Y and one ormore of Z.

Various modifications and additions can be made without departing fromthe spirit and scope of this invention. Features of each of the variousembodiments described above may be combined with features of otherdescribed embodiments as appropriate in order to provide a multiplicityof feature combinations in associated new embodiments. Furthermore,while the foregoing describes a number of separate embodiments, what hasbeen described herein is merely illustrative of the application of theprinciples of the present invention. Additionally, although particularmethods herein may be illustrated and/or described as being performed ina specific order, the ordering is highly variable within ordinary skillto achieve aspects of the present disclosure. Accordingly, thisdescription is meant to be taken only by way of example, and not tootherwise limit the scope of this invention.

Exemplary embodiments have been disclosed above and illustrated in theaccompanying drawings. It will be understood by those skilled in the artthat various changes, omissions and additions may be made to that whichis specifically disclosed herein without departing from the spirit andscope of the present invention.

What is claimed is:
 1. A spinal curve modulation system for treatingspinal curvature along a treatment region of the spine, comprising: aflexible tether of sufficient length to extend across the treatmentregion of the spine including across at least three adjacent vertebralbodies in a cranial-caudal direction; at least one first bone anchorconfigured to be fixed to a first vertebra and to the flexible tether; atether tensioning unit comprising a tether interface member rotatablearound a rotation axis and a remotely operable rotary drive operativelylinked to the tether interface member to adjust tension in the flexibletether, said tension applied to the flexible tether in a directionperpendicular to the rotation axis; and at least one second bone anchorhaving a longitudinal axis perpendicular to the rotation axis andconfigured to fix the tether tensioning unit to a vertebra across thetreatment region from at said at least one first bone anchor; whereinsaid tether tensioning unit is actuatable to adjust tension in theflexible tether without surgically exposing the flexible tether, said atleast one first bone anchor or said at least one second bone anchor. 2.The spinal curve modulation system of claim 1, further comprising pluralfirst bone anchors, wherein the first bone anchors are configured forfixed attachment to the flexible tether at plural locations along theflexible tether.
 3. The spinal curve modulation system of claim 1,wherein said first bone anchors comprise: a threaded body portion with atip configured to penetrate bone; a head portion disposed on thethreaded body portion opposite the tip, wherein said head portion has athreaded top, and defines an open window for passing the flexible tethertherethrough and an upwardly open slot extending across the head portiontransverse to the open window; a tether pin configured to be received insaid upwardly open slot extending across the open window; and a tetherpin cap with an internal thread configured to engage said threaded topand retain the tether pin in said upwardly open slot.
 4. The spinalcurve modulation system of claim 3, wherein said open window is formedas a second upwardly open slot such that the head portion comprises fourthreaded pillars, whereby the tether pin with the flexible tetherwrapped therearound may be placed in the second upwardly open slot tosecure the flexible tether thereto without having to pass an end of theflexible tether through the open window.
 5. The spinal curve modulationsystem of claim 1, wherein said first bone anchors comprise: a threadedbody portion with a tip configured to penetrate bone; a head portiondisposed on the threaded body portion opposite the tip, wherein saidhead portion comprises two opposed side walls defining an open slottherebetween; and a tether pin extending across the open slot betweenthe opposed side wall.
 6. The spinal curve modulation system of claim 5,wherein: said side walls each have an inwardly facing recess; and thetether pin is removable and configured to be received in and retained bysaid inwardly facing recesses.
 7. The spinal curve modulation system ofclaim 5, wherein: said side walls define transverse openings; and thetether pin is removable and configured to be received in and retained bysaid transverse openings.
 8. The spinal curve modulation system of claim7, wherein the tether pin includes at least one retaining gasket on atleast one end, said retaining gasket configured to engage an innercircumference of at least one said transvers openings to retain thetether pin therein.
 9. The spinal curve modulation system of claim 7,wherein the tether pin includes an external thread on at least one endand at least one said transverse opening is formed with an internalthread configured to mate with the tether pin external thread.
 10. Thespinal curve modulation system of claim 1, wherein said first boneanchors comprise: a threaded body portion with a tip configured topenetrate bone; a tether pin with a first end, a central portionconfigured to permit the flexible tether to be wrapped therearound, anda second end with a radially directed side wall; and a head portiondisposed on the threaded body portion opposite the tip configured toreceive and support the tether pin, wherein— said head portion comprisesfirst and second side walls forming an open slot therebetween with areceptacle slot formed in the first side wall opening towards a side ofthe head portion and an upwardly extending stop formed by the secondwall, the tether pin first end is configured to be received in saidreceptacle slot, a pivot pin is disposed on the tether pin radiallydirected side wall spaced from the central portion of the tether pin,and a pivot hole configured to receive the pivot pin is formed in thesecond side wall adjacent a lower end of the upwardly extending stop;whereby the flexible tether is secured by wrapping around the tether pincentral portion and the tether pin pivoted such that the first end ofthe tether pin is captured in the receptacle slot and the extension wallof the tether pin is butted up against the side wall of the headportion.
 11. The spinal curve modulation system of claim 1, wherein saidfirst bone anchors comprise: a threaded body portion with a tipconfigured to penetrate bone; a head portion disposed on the threadedbody portion opposite the tip, wherein said head portion comprises firstand second side walls forming an open slot therebetween with the firstside wall defining a receptacle pocket and the second side wall ispivotable outward with respect to the open slot; and a tether pindisposed on the second side wall extending towards the first side walland configured to be received in the receptacle pocket of the first sidewall.
 12. The spinal curve modulation system of claim 1, wherein saidtether interface comprises a tether interface spool engageable with therotary drive, the tether interface spool having two spool end flangeswith a spool axel disposed therebetween, the spool axel defining an openslot configured for the flexible tether to pass through.
 13. The spinalcurve modulation system of claim 12, wherein the flexible tether hassufficient length to pass through said slot and wrap around at least aportion of the spool axel with both tether ends secured at a common boneanchor.
 14. The spinal curve modulation system of claim 1, furthercomprising at least one tether guide having a bone anchor and a guideportion configured to slidably receive the flexible tether, wherein theguide portion comprises a head defining an opening through which theflexible tether may slide along a longitudinal direction.
 15. The spinalcurve modulation system of claim 14, wherein the guide portion of thetether guide comprises the head formed with opposed side walls definingan open slot therebetween, the head having screw external threads at anupper end configured to receive a threaded cap thereon.
 16. The spinalcurve modulation system of claim 14, wherein the guide portion of thetether guide comprises the head formed with opposed side walls definingan open slot therebetween, each said side wall including a portion of afemale threaded hole such that a threaded plug can be screwed in betweenthe opposed side walls.
 17. A bone anchor for securing a flexible tetherto exert force on a bone, comprising, a threaded body portion with a tipconfigured to be screwed into bone; and a head portion disposed on thethreaded body portion opposite the tip; wherein the head portioncomprises means for securing the flexible tether.
 18. The bone anchor ofclaim 17, wherein said means for securing the tether comprises: athreaded top formed on the head portion; an open window defined in thehead portion under the threaded top for passing the tether therethrough;an upwardly open slot extending across the head portion transverse tothe open window; a tether pin configured to be received in said upwardlyopen slot extending across the open window; and a tether pin cap with aninternal thread configured to engage said threaded top and retain thetether pin in said upwardly open slot.
 19. The bone anchor of claim 18,wherein said open window is formed as a second upwardly open slot suchthat the head portion comprises four threaded pillars, whereby thetether pin with the flexible tether wrapped therearound may be placed inthe second upwardly open slot to secure the flexible tether theretowithout having to pass the flexible tether through the open window. 20.The bone anchor of claim 17, wherein said means for securing the tethercomprises: two opposed side walls formed in the head portion defining anopen slot therebetween; and a tether pin extending across the open slotbetween the opposed side wall.
 21. The bone anchor of claim 20, wherein:said side walls each have an inwardly facing recess; and the tether pinis configured to be received in and retained by said inwardly facingrecesses.
 22. The bone anchor of claim 20, wherein: said side wallsdefine transverse openings; and a tether pin configured to be receivedin and retained by said transverse openings.
 23. The bone anchor ofclaim 22, wherein said means for securing the tether further comprisesat least one retaining gasket on at least one end of the tether pin,said retaining gasket configured to engage an inner circumference of atleast one said transvers openings to retain the tether pin therein. 24.The bone anchor of claim 22, wherein said means for securing the tetherfurther comprises an external thread on at least one end of the tetherpin and at least one said transverse opening is formed with an internalthread configured to mate with the tether pin external thread.
 25. Thebone anchor of claim 17, wherein said means for securing the tethercomprises: first and second side walls formed in the head portiondefining an open slot therebetween with a receptacle slot formed in thefirst side wall opening towards a side of the head portion and anupwardly extending stop formed by the second wall; a tether pin with afirst end, a central portion configured to permit the flexible tether tobe wrapped therearound, and a second end with a radially directed sidewall, wherein the tether pin first end is configured to be received insaid receptacle slot; a pivot pin disposed on said radially directedside wall spaced from the central portion of the pivot pin; and a pivothole configured to receive the pivot pin formed in the second side walladjacent a lower end of the upwardly extending stop; whereby theflexible tether is secured by wrapping around the tether pin centralportion and the tether pin pivoted such that the first end of the tetherpin is captured in the receptacle slot and the extension wall of thetether pin is butted up against the side wall of the head portion. 26.The bone anchor of claim 17, wherein said means for securing the tethercomprises: first and second side walls formed in the head portiondefining an open slot therebetween with the first side wall defining areceptacle pocket and the second side wall pivotable outward withrespect to the open slot; and a tether pin disposed on the second sidewall extending towards the first side wall and configured to be receivedin the receptacle pocket of the first side wall.
 27. A method oftreating an abnormal spinal curvature along a treatment region of thespine, comprising: providing surgical access to the treatment region ofthe spine, the treatment region extending along the spine in a generallycranial-caudal direction and spanning at least three adjacent vertebrae;fixing a first bone anchor on a selected vertebra at a first end of thetreatment region; fixing a second bone anchor having a longitudinal axison a selected second vertebra spaced across the treatment region fromthe first bone anchor; fixing at least one third bone anchor on aselected vertebra between the first and second bone anchors; attaching atether tension adjustment mechanism to the second bone anchor afterfixing the second bone anchor to the selected second vertebra; extendinga flexible tether between said tension adjustment mechanism and thefirst bone anchor; fixing the flexible tether to the at least one thirdbone anchor; manipulating said tension adjustment mechanism to initiallytension the flexible tether so as to reposition vertebrae across thetreatment region; closing the surgical access to the treatment region ofthe spine; and post-operatively, subsequent to closing the surgicalaccess and without reopening or creating new surgical access to theflexible tether or bone anchors, manipulating said tension adjustmentmechanism in vivo to periodically adjust tension in the flexible tether.28. The method of claim 27, wherein: the tether tension adjustmentmechanism comprises a rotatable tether interface spool with a spool axeldefining a slot; and said step of extending the flexible tether betweensaid tension adjustment mechanism and the first bone anchor comprisespassing an end of the flexible tether through said spool axel slot andwrapping the flexible tether around at least a portion of the spoolaxel.
 29. The method of claim 27, wherein: said post-operativelymanipulating said rotary member comprises driving the rotary member witha wirelessly controllable motor under control of a remote, wirelesscontroller external to the body; and said wirelessly controllable motorcomprises a magnetic motor and said manipulating the wirelesslycontrollable motor comprises rotating at least one magnet in saidremote, wireless controller.